This invention relates to titanium oxide particles of specified shapes and processes for production thereof. More particularly, the invention relates to titanium oxide particles that are fan- or disk-shaped and which have a sufficiently high ultraviolet blocking effect (in particular, uv-A blocking effect) and high enough dispersibility and transparency to be useful as uv inhibitors in sunblock cosmetics, uv inhibiting paints, plastics and so forth. The invention also relates to processes for producing such titanium oxide particles.
Conventionally, ultrafine titanium oxide powders having a primary particle size of no more than 0.1 .mu.m are commonly used in sunblock cosmetics, uv inhibiting paints, plastics and so forth with a view to providing an enhanced uv inhibiting effect.
However, ultrafine titanium oxide particles not larger than 0.1 .mu.m are prone to agglomeration and producing a uniform dispersion of primary particles requires considerable effort and is sometimes impossible to accomplish.
Cosmetics incorporating ultrafine titanium oxide particles are effective in inhibiting uv-B (280-320 nm) but little effective in inhibiting uv-A (320-380 nm). If an increased amount of such titanium oxide particles is incorporated with a view to inhibiting uv-A, ease in use is inevitably compromised as exemplified by graininess and poor spreadability.
Thus, many problems are encountered in applying ultrafine titanium oxide particles to the purpose of blocking ultraviolet rays, particularly uv-A, and there has been a strong need to develop highly dispersible titanium oxide particles that have a high uv-A blocking effect and which are also transparent.